Turbine and turbofan engines provide energy for a wide range of applications. FIG. 1 is a block schematic diagram of a typical turbofan engine 100. The turbofan engine 100 comprises an inlet fan 101, a compressor 103, a combustor 105, a high-pressure turbine 107, a low-pressure turbine 109, a bypass region 111, and an exhaust mixing region 113. The inlet fan 101 is mounted to the front of the compressor 103. The engine core 115 is defined as the compressor 103, combustor 105, high-pressure turbine 107, and low-pressure turbine 109. Turboshaft engines have a similar arrangement to the turbofan engine 100 illustrated in FIG. 1, but typically do not include an inlet fan 101.
Air enters the turbofan engine 100 via inlet fan 101. A first portion of the air flows through the bypass region 111 and into the exhaust mixing region 113. A second portion of the air flows into the compressor 103 where it is pressurized, then into the combustor where it is mixed with fuel and ignited. The ratio of the first portion of air flowing through the bypass region 111 to the second portion of air flowing through the engine core 115 is referred to as the bypass ratio.
The hot, high-pressure combustion gasses are directed sequentially into the high-pressure turbine 107 and low-pressure turbine 109, causing each turbine 107, 109 to rotate about a shaft which is connected to and drives the compressor 103 and the inlet fan 101. In multiple-spool designs, more than one concentric shafts are used to separately rotate various components. For example, in a standard two-spool turbofan engine the high-pressure turbine 107 and at least a portion of compressor 103 are connected using a first common shaft (often referred to as the high pressure shaft) while the low-pressure turbine 109 and inlet fan 101 are connected using a second common shaft (often referred to as the low pressure shaft). A portion of compressor 103 may also be connected to the second common shaft.
Engine components which rotate at relatively high speeds include the inlet fan 101, the high pressure compressor 103, the high-pressure turbine 107, the low-pressure turbine 109, and the one or more shafts. These rotating components are generally supported by lubricated components such as bearings. Lubricant is supplied under pressure to the lubricated components and a sump, either rotating with the rotating components or stationary (non-rotating) is often disposed about the lubricated component to collect (scavange) the lubricant expelled from the lubricated component.
Lubricant scavenging in the vicinity of a rotating shaft can be problematic. Shaft rotation causes air inside the lubricant sump to rotate in the same direction as the shaft, which tends to force lubricant droplets exiting a lubricated component to form a thin lubricant film on a radially-inner surface of the sump. The momentum of the lubricant droplets and the force of the rotating air (windage) inside the sump will drive the lubricant film around the circumference of the radially-inner surface of the sump, which makes it difficult to direct the lubricant film into a collection point.
This difficulty and complexity of collecting lubricant is exacerbated in an engine having counter-rotating shafts. Two zones of rotating air are formed, one in the vicinity of each shaft. Where these zones come together, vortices and complex air flow patterns are formed.
Previous attempts to collect lubricant in this complex environment have included the use of multiple collection points which leads to a further problem of needing to transfer the lubricant to a single point for pressurization and distribution back to the lubricated component. Other attempts have included the use of multiple collection points leading to multiple reservoirs, which necessitates additional lines and pumps to distribute the lubricant to one or more lubricated components. These extra parts incur a weight penalty that can be significant for some turbine engine applications such as aviation, undesirably add to the complexity of the engine design, and increase the need and cost of system maintenance.
There is thus a need in the art for an improved lubricant scavenge system which overcomes the deficiencies noted above, particularly as they relate to a tubine engine having counter-rotating shafts.
The present application discloses one or more of the features recited in the appended claims and/or the following features which, alone or in any combination, may comprise patentable subject matter.